Behavioral syndromes and the evolution of correlated behavior in zebrafish

Studies of "behavioral syndromes" in different populations andspecies of animals can be used to shed light on the underlyingmechanisms of evolution. For example, some personality syndromessuggest the existence of an underlying hormonal link, whereasother relationships between boldness and aggression appear tobe the result of similar selective pressures. Here, we used1 wild-derived and 2 laboratory strains of zebrafish (Daniorerio) to examine relationships among 5 behavioral measures:shoaling, activity level, predator approaches, latency to feedafter a disturbance, and biting to a mirror stimulus. We foundevidence of an activity syndrome, as if underlying metaboliccosts influence variation in multiple forms of behavior. Evidencefor a relationship between boldness and aggression was alsoapparent but depended both on strain and which specific behaviorpatterns were identified as measures of "boldness." Althoughsome comparisons of laboratory and wild-derived strains wereconsistent with a domestication syndrome, others were not. Mostobserved relationships were relatively weak and occasionallyinconsistent, arguing against strong underlying genetic linkagesor pleiotropic effects relating any of the behavioral measures.Instead, it may be more important to study the details of selectivecontext or the long-term impact of linkages between some, butnot all, of a large set of genes influencing complex behavioraltraits. We found profound differences among strains in mostbehavior patterns, but few sex differences. One strain (TM1)was consistently different from the others (SH and Nadia) beingmore social, more likely to approach predators, and taking lesstime to recover from disturbance than were the other 2 strains.     

Rapid parallel evolution of aberrant traits in the diversification of the Gulf of Guinea white-eyes (Aves, Zosteropidae)

Archipelago-endemic bird radiations are familiar to evolutionary biologists as key illustrations of evolutionary patterns. However, such radiations are in fact rare events. White-eyes (Zosteropidae) are birds with an exceptionally high colonization and speciation potential; they have colonized more islands globally than any other passerine group and include the most species-rich bird genus. The multiplication of white-eye island endemics has been consistently attributed to independent colonizations from the mainland; the white-eyes of the Gulf of Guinea archipelago had been seen as a classic case, spanning as great a breadth of phenotypic diversity as the family worldwide. Contrary to this hypothesis, our molecular phylogenetic analysis places the Gulf of Guinea white-eyes in just two radiations, one grouping all five oceanic island taxa and the other grouping continental island and land-bridge taxa. Numerous 'aberrant' phenotypes (traditionally grouped in the genus Speirops) have evolved independently over a short space of time from nonaberrant (Zosterops) phenotypes; the most phenotypically divergent species have separated as recently as 0.22 Ma. These radiations rival those of Darwin's finches and the Hawaiian honeycreepers in terms of the extent of adaptive radiation per unit time, both in terms of species numbers and in terms of phenotypic diversity. Tempo and patterns of morphological divergence are strongly supportive of an adaptive radiation in the oceanic islands driven by ecological interactions between sympatric white-eyes. Here, very rapid phenotypic evolution mainly affected taxa derived from the youngest wave of colonization, in accordance with the model of asymmetric divergence owing to resource competition in sympatry.     

Capital and income breeding and the evolution of colony founding strategies in ants

Ability to store resources that will be used for reproduction represents a potential life history adaptation because storage permits feeding and reproduction to be decoupled spatially and/or temporally. The two ends of a continuum involve acquiring all resources prior to reproduction (capital breeding) or acquiring all resources during the reproductive period (income breeding). Traditional life history theory examines tradeoffs between costs and benefits of such strategies, but this theory has not been integrated into life history studies of ants, even though founding queens have the analogous strategies of fully claustral (capital breeding) and semi-claustral (income breeding). This study demonstrates that facultatively semi-claustral queens of the seed-harvester ant Pogonomyrmex desertorum exhibit phenotypic plasticity during colony founding because unfed queens produced few, small minims, whereas ad libitum fed queens produced larger, heavier minims and additional brood. Fed queens also lost less mass than unfed queens despite their producing more brood. Overall, foraging provides queens with a suite of benefits that likely offset potential negative effects of foraging risk. Life history studies across a diverse array of taxa show that capital breeding is consistently associated with low availability and/or unpredictability of food, i.e., environmental conditions that favor prepackaging of reproductive resources. Such a broad and consistent pattern suggests that similar factors favored the evolution of fully claustral (capital breeding) colony founding in ants. Overall, these data suggest that ant researchers should revise their conventional view that fully claustral colony founding evolved because it eliminated the need for queens to leave the nest to forage. Instead, colony founding strategies should be examined from the perspective of environmental variation, i.e., availability and predictability of food. I also provide a functional scenario that could explain the evolution of colony founding strategies in ants. Received 16 November 2005; revised 1 March 2006; accepted 29 March 2006.     

Functional genetics of intraspecific ecological interactions in Arabidopsis thaliana

Studying the genetic basis of traits involved in ecological interactions is a fundamental part of elucidating the connections between evolutionary and ecological processes. Such knowledge allows one to link genetic models of trait evolution with ecological models describing interactions within and between species. Previous work has shown that connections between genetic and ecological processes in Arabidopsis thaliana may be mediated by the fact that quantitative trait loci (QTL) with 'direct' effects on traits of individuals also have pleiotropic 'indirect' effects on traits expressed in neighbouring plants. Here, we further explore these connections by examining functional relationships between traits affected directly and indirectly by the same QTL. We develop a novel approach using structural equation models (SEMs) to determine whether observed pleiotropic effects result from traits directly affected by the QTL in focal individuals causing the changes in the neighbours' phenotypes. This hypothesis was assessed using SEMs to test whether focal plant phenotypes appear to mediate the connection between the focal plants' genotypes and the phenotypes of their neighbours, or alternatively, whether the connection between the focal plants' genotypes and the neighbours' phenotypes is mediated by unmeasured traits. We implement this analysis using a QTL of major effect that maps to the well-characterized flowering locus, FRIGIDA. The SEMs support the hypothesis that the pleiotropic indirect effects of this locus arise from size and developmental timing-related traits in focal plants affecting the expression of developmental traits in their neighbours. Our findings provide empirical insights into the genetics and nature of intraspecific ecological interactions. Our technique holds promise in directing future work into the genetic basis and functional relationship of traits mediating and responding to ecological interactions.     

Kinship rivalry does not trigger specific allocation strategies in Lupinus angustifolius

Background and Aims

Research on the ability of plants to recognize kin and modify plant development to ameliorate competition with coexisting relatives is an area of very active current exploration. Empirical evidence, however, is insufficient to provide a sound picture of this phenomenon.

Methods

An experiment was designed to assess multi-trait phenotypic expression in response to competition with conspecifics of varied degrees of genealogical relatedness. Groups of siblings, cousins and strangers of Lupinus angustifolius were set in competition in a pots assay. Several whole-plant and organ-level traits, directly related to competition for above- and below-ground resources, were measured. In addition, group-level root proliferation was measured as a key response trait to relatedness to neighbours, as identified in previous work.

Key Results

No major significant phenotypic differences were found between individuals and groups that could be assigned to the gradient of relatedness used here. This occurred in univariate models, and also when multi-trait interactions were evaluated through multi-group comparisons of Structural Equation Models. Root proliferation was higher in phenotypically more heterogeneous groups, but phenotypic heterogeneity was independent of the relatedness treatments of the experiment, and root proliferation was alike in the neighbourhoods of siblings, cousins and strangers.

Conclusions

In contrast to recent findings in other species, genealogical relatedness to competing neighbours has a negligible impact on the phenotypic expression of individuals and groups of L. angustifolius. This suggests that kin recognition needs further exploration to assess its generality, the ecological scenarios where it might have been favoured or penalized by natural selection, and its preponderance in different plant lineages.     

Reproductive competition and the evolution of extreme birth synchrony in a cooperative mammal

Reproductive events in animal societies often show a high degree of temporal clustering, but the evolutionary causes of this synchronization are poorly understood. Here, we suggest that selection to avoid the negative effects of competition with other females has given rise to a remarkable degree of birth synchrony in the communal-breeding banded mongoose (Mungos mungo). Within banded mongoose groups, births are highly synchronous, with 64 per cent of females giving birth on exactly the same night. Our results indicate that this extreme synchrony arises because offspring suffer an increased risk of infanticide if their mother gives birth before other females, but suffer in competition with older littermates if their mother gives birth after them. These findings highlight the important influence that reproductive competition can have for the evolution of reproductive synchrony.     

Leaf trait relationships of native and invasive plants: community- and global-scale comparisons

Leaf carbon capture strategies of native and exotic invasive plants were compared by examining leaf traits and their scaling relationships at community and global scales. Community-level leaf trait data were obtained for 55 vascular plant species from nutrient-enriched and undisturbed bushland in Sydney, Australia. Global-scale leaf trait data were compiled from the literature for 75 native and 90 exotic invasive coexisting species. At the community level, specific leaf area (SLA), foliar nitrogen and phosphorus (N(mass) and P(mass)) and N:P ratio were significantly higher for exotics at disturbed sites compared with natives at undisturbed sites, with natives at disturbed sites being intermediate. SLA, N(mass) and P(mass) were positively correlated, with significant shifts in group means along a common standardized major axis (SMA) slope. At the global scale, invasives had significantly higher N(mass), P(mass), assimilation rate (A(mass) and A(area)) and leaf area ratio (LAR) than natives. All traits showed positive correlations, with significant shifts in group means along a common slope. For a given SLA, invasives had higher A(mass) (7.7%) and N(mass) (28%). Thus, exotic invasives do not have fundamentally different carbon capture strategies from natives but are positioned further along the leaf economics spectrum towards faster growth strategies. Species with leaf traits enabling rapid growth will be successful invaders when introduced to novel environments where resources are not limited.     

匍匐茎草本植物形态可塑性、整合作用与觅食行为研究进展

综述了匍匐茎型克隆植物在形态可塑性、整合作用及觅食行为方面的研究进展。资源斑块性分布是生境异质性的特征之一,适应于异质性生境,匍匐茎植物对环境资源表现了一系列可塑性反应。本文着重从匍匐茎植物对光、水、肥的可塑性反应及其整合作用以及觅食行为等方面的研究进行总结分析,以期对匍匐茎型克隆植物进行更广泛深入的研究。     

Using archaeogenomic and computational approaches to unravel the history of local adaptation in crops

Our understanding of the evolution of domestication has changed radically in the past 10 years, from a relatively simplistic rapid origin scenario to a protracted complex process in which plants adapted to the human environment. The adaptation of plants continued as the human environment changed with the expansion of agriculture from its centres of origin. Using archaeogenomics and computational models, we can observe genome evolution directly and understand how plants adapted to the human environment and the regional conditions to which agriculture expanded. We have applied various archaeogenomics approaches as exemplars to study local adaptation of barley to drought resistance at Qasr Ibrim, Egypt. We show the utility of DNA capture, ancient RNA, methylation patterns and DNA from charred remains of archaeobotanical samples from low latitudes where preservation conditions restrict ancient DNA research to within a Holocene timescale. The genomic level of analyses that is now possible, and the complexity of the evolutionary process of local adaptation means that plant studies are set to move to the genome level, and account for the interaction of genes under selection in systems-level approaches. This way we can understand how plants adapted during the expansion of agriculture across many latitudes with rapidity.     

Inter-relationships between standing crop, biodiversity and trait attributes of hydrophytic vegetation in artificial waterways

1. The extensive British canal system potentially provides a favourable habitat for aquatic plants and, because of its uniformity, it is ideal for studying relationships between disturbance intensity (largely from boat traffic) and communities of aquatic macrophytes. 2. The standing crop and species composition of aquatic plants were measured in summer at 396 sites distributed randomly over the canal network. We also quantified the number of rare species and ‘attribute groups’ (groups of species sharing similar suites of biological traits). These data were analysed in relation to standing crop, assumed to indicate a disturbance gradient. 3. Consistent with unimodal models and the Intermediate Disturbance Hypothesis, maximum hydrophyte species richness occurred at an intermediate biomass (50–200 g DWm^?2). This corresponded to a low frequency of low magnitude disturbance (light boat traffic) on navigable sections, or occasional high magnitude disturbance (the post‐interventionist phase) on sections currently unnavigable and subject to active vegetation management. The frequency of rare species was also the greatest under these conditions, reflecting the availability of regeneration niches. 4. Sorting of species into attribute groups revealed that the overall relationship between species richness and standing crop comprised of closely overlapping unimodal responses of nine attribute groups, superimposed on a core vegetation of Potamogeton pectinatus, together with greater representation of filamentous algae, lemnids and elodeids with increasing standing crop (i.e. assumed low disturbance). High species richness was associated with the overlap of functionally different groups of species, rather than with disturbance‐mediated coexistence of functionally similar plants. 5. The analysis of a matrix of sites and the representation of plant traits weighted by the biomass of species that displayed them, in relation to different aspects of disturbance, highlighted a shift from traits associated with resilience (turions, unanchored floating or submerged leaves, low body flexibility, budding, small body size), or competitiveness (entire leaves, low reproductive output, high biomass density, large body size) at high standing crop, through to attributes more associated with resistance to disturbance (rhizomes, tubers, streamlining of foliage, low biomass density) at low standing crop. 6. Comparison with a stochastic null model of change in species number along a constrained gradient, after correction for variation in sampling effort, indicated that sites towards the tails of the gradient (excluding those with extremely low biomass) supported more species than might be expected from chance alone, while the most species‐rich sites in mid‐gradient generally supported many fewer species than expected. 7. We suggest that a disturbance regime that maintains intermediate standing crops would be appropriate for the conservation of species‐rich aquatic vegetation. Precise definition of this regime, under a range of circumstances, requires the study of temporal change at representative sites.     

New perspectives on the evolution of plant mating systems

BACKGROUND: The remarkable diversity of mating patterns and sexual systems in flowering plants has fascinated evolutionary biologists for more than a century. Enduring questions about this topic include why sexual polymorphisms have evolved independently in over 100 plant families, and why proportions of self- and cross-fertilization often vary dramatically within and among populations. Important new insights concerning the evolutionary dynamics of plant mating systems have built upon a strong foundation of theoretical models and innovative field and laboratory experiments. However, as the pace of advancement in this field has accelerated, it has become increasingly difficult for researchers to follow developments outside their primary area of research expertise. SCOPE: In this Viewpoint paper we highlight three important themes that span and integrate different subdisciplines: the changes in morphology, phenology, and physiology that accompany the transition to selfing; the evolutionary consequences of pollen pool diversity in flowering plants; and the evolutionary dynamics of sexual polymorphisms. We also highlight recent developments in molecular techniques that will facilitate more efficient and cost-effective study of mating patterns in large natural populations, research on the dynamics of pollen transport, and investigations on the genetic basis of sexual polymorphisms. This Viewpoint also serves as the introduction to a Special Issue on the Evolution of Plant Mating Systems. The 15 papers in this special issue provide inspiring examples of recent discoveries, and glimpses of exciting developments yet to come.     

The evolution of phenotypic plasticity in spatially structured environments: implications of intraspecific competition, plasticity costs and environmental characteristics

We model the evolution of reaction norms focusing on three aspects: frequency-dependent selection arising from resource competition, maintenance and production costs of phenotypic plasticity, and three characteristics of environmental heterogeneity (frequency of environments, their intrinsic carrying capacity and the sensitivity to phenotypic maladaptation in these environments). We show that (i) reaction norms evolve so as to trade adaptation for acquiring resources against cost avoidance; (ii) maintenance costs cause reaction norms to better adapt to frequent rather than to infrequent environments, whereas production costs do not; and (iii) evolved reaction norms confer better adaptation to environments with low rather than with high intrinsic carrying capacity. The two previous findings contradict earlier theoretical results and originate from two previously unexplored features that are included in our model. First, production costs of phenotypic plasticity are only incurred when a given phenotype is actually produced. Therefore, they are proportional to the frequency of environments, and these frequencies thus affect the selection pressure to avoid costs just as much as the selection pressure to improve adaptation. This prevents the frequency of environments from affecting the evolving reaction norm. Secondly, our model describes the evolution of plasticity for a phenotype determining an individual's capability to acquire resources, and thus its realized carrying capacity. When individuals are distributed randomly across environments, they cannot avoid experiencing environments with intrinsically low carrying capacity. As selection pressures arising from the need to improve adaptation are stronger under such extreme conditions than under mild ones, better adaptation to environments with low rather than with high intrinsic carrying capacity results.     

我国植物种群生态研究的成就与展望

种群生态学以种群作为研究对象,无论在理论上还是在方法上都是生态学中发展最快,最为活跃的一个领域,也是生态学研究中的一个极其重要的层次,因为它是物种存在和进化的基本单位,是生物群落和生态系统的基本组成。一、植物种群生态学研究的历史Graunt于1662年进行了人类种群的生命     

Mapping behavioural evolution onto brain evolution: the strategic roles of conserved organization in individuals and species

The pattern of individual variation in brain component structure in pigs, minks and laboratory mice is very similar to variation across species in the same components, at a reduced scale. This conserved pattern of allometric scaling resembles robotic architectures designed to be robust to changes in computing power and task demands, and may reflect the mechanism by which both growing and evolving brains defend basic sensory, motor and homeostatic functions at multiple scales. Conserved scaling rules also have implications for species-specific sensory and social communication systems, motor competencies and cognitive abilities. The role of relative changes in neuron number in the central nervous system in producing species-specific behaviour is thus highly constrained, while changes in the sensory and motor periphery, and in motivational and attentional systems increase in probability as the principal loci producing important changes in functional neuroanatomy between species. By their nature, these loci require renewed attention to development and life history in the initial organization and production of species-specific behavioural abilities.     

Population genetic models can be used to study the evolution of the interacting behaviours of parents and their progeny

An example of the evolution of the interacting behaviours of parents and progeny is studied using iterative equations linking the frequencies of the gametes produced by the progeny to the frequencies of the gametes in the parental generation. This population genetics approach shows that a model in which both behaviours are determined by a single locus can lead to a stable equilibrium in which the two behaviours continue to segregate. A model in which the behaviours are determined by genes at two separate loci leads eventually to fixation of the alleles at both loci but this can take many generations of selection. Models of the type described in this paper will be needed to understand the evolution of complex behaviour when genomic or experimental information is available about the genetic determinants of behaviour and the selective values of different genomes.     

Constraints on the evolution of adaptive plasticity: costs of plasticity to density are expressed in segregating progenies

Phenotypic plasticity, the ability of a genotype to express different phenotypes across environments, is an adaptive strategy expected to evolve in heterogeneous environments. One widely held hypothesis is that the evolutionary benefits of plasticity are reduced by its costs, but when compared with the number of traits tested, the evidence for costs is limited. Selection gradients were calculated for traits and trait plasticities to test for costs of plasticity to density in a field study using recombinant inbred lines (RILs) of Brassica rapa. Significant costs of putatively adaptive plasticity were found in three out of six measured traits. For one trait, petiole length, a cost of plasticity was detected in both environments tested; such global costs are expected to more strongly constrain the evolution of plasticity than local costs expressed in a single environment. These results, in combination with evidence from studies in segregating progenies of Arabidopsis thaliana, suggest that the potential for genetic costs of plasticity exists in natural populations. Detection of costs in previous studies may have been limited because historical selection has purged genotypes with costly plasticity, and experimental conditions often lack environmental stresses.     

Testing for non-randomness in sizes and habitats of West Indian lizards: choice of species pool affects conclusions from null models

Summary Several null models are proposed for testing whether size or habitat differences in West IndianAnolis lizards are greater than expected by chance. The models differ primarily in choice of the pool from which species are sampled to form random communities. Regardless of choice of pool, size differences in the Lesser Antilles are greater than null models predict; the pool using species on the known source (Puerto Rico) gives a greater variance in ratios but about the same mean ratio (for males), or a greater mean ratio (for females), compared with the pool composed of species on the islands being tested (the Stronget al., 1979, Galápagos procedure). On satellite islands of the Greater Antilles, sizes do not differ more than expected from null models. Pools composed of mainland-source species give null communities with more small or more large ratios than those composed of island species, depending upon whether four-species islands are included or excluded, respectively. Colwell and Winkler's unmodified Narcissus hypothesis is contradicted by these results in procedures where species not likely to be able to occur on small islands are included in the species pool. Using the most biologically reasonable, but not other, choices of source pool, species on satellite islands of the Greater Antilles differ more in structural habitat then expected by chance. In contrast to some of the results on size, here mainland-source pools are more likely to produce a statistically significant difference between real and random communities, as predicted by the Narcissus hypothesis. However, exclusion of structural habitat categories not found on satellite islands is necessary to achieve this significance.     

The evolution of cooperative breeding in birds: kinship,dispersal and life history

The evolution of cooperation among animals has posed a major problem for evolutionary biologists, and despite decades of research into avian cooperative breeding systems, many questions about the evolution of their societies remain unresolved. A review of the kin structure of avian societies shows that a large majority live in kin-based groups. This is consistent with the proposed evolutionary routes to cooperative breeding via delayed dispersal leading to family formation, or limited dispersal leading to kin neighbourhoods. Hypotheses proposed to explain the evolution of cooperative breeding systems have focused on the role of population viscosity, induced by ecological/demographic constraints or benefits of philopatry, in generating this kin structure. However, comparative analyses have failed to generate robust predictions about the nature of those constraints, nor differentiated between the viscosity of social and non-social populations, except at a coarse level. I consider deficiencies in our understanding of how avian dispersal strategies differ between social and non-social species, and suggest that research has focused too narrowly on population viscosity and that a broader perspective that encompasses life history and demographic processes may provide fresh insights into the evolution of avian societies.     

Rates of phenotypic evolution of ecological characters and sexual traits during the Tanganyikan cichlid adaptive radiation

Theory suggests that sexual traits evolve faster than ecological characters. However, characteristics of a species niche may also influence evolution of sexual traits. Hence, a pending question is whether ecological characters and sexual traits present similar tempo and mode of evolution during periods of rapid ecological divergence, such as adaptive radiation. Here, we use recently developed phylogenetic comparative methods to analyse the temporal dynamics of evolution for ecological and sexual traits in Tanganyikan cichlids. Our results indicate that whereas disparity in ecological characters was concentrated early in the radiation, disparity in sexual traits remained high throughout the radiation. Thus, closely related Tanganyikan cichlids presented higher disparity in sexual traits than ecological characters. Sexual traits were also under stronger selection than ecological characters. In sum, our results suggest that ecological characters and sexual traits present distinct evolutionary patterns, and that sexual traits can evolve faster than ecological characters, even during adaptive radiation.